A giant magnetoresistive element (Giant MagnetoResistive: GMR) has provided a dramatic improvement of the performance of a magnetic device, e.g., a magnetic head in particular. In other words, a spin valve film (Spin Valve: SV film) of all others was applied to the magnetic head, MRAM (Magnetic Random Access Memory), etc. to have brought a major advance to the technical field of magnetic devices.
The “spin valve film” is a laminated film having a nonmagnetic layer (called a “spacer layer”) sandwiched between two ferromagnetic layers. One of the two magnetic layers has its magnetization fixed by an antiferromagnetic layer, and is called a “pinned layer” or a “magnetization fixed layer”. The other has magnetization rotatable in response to an external magnetic field, and is called a “free layer” or a “magnetization free layer”. The spin valve film provides a change in the electrical resistance due to a change in the relative angle between the magnetization directions of the pinned layer and the free layer. The rate of the resistance change is called an MR (MagnetoResistance) change rate, and corresponds to an output of magnetic elements or devices.
A magnetoresistive element is disclosed in a Japanese laid-open patent application (see, for example, JP-A 2006-108631), which sandwiches a lamination structure between electrodes including Cr or Au. The lamination structure has a nonmagnetic layer of Cu sandwiched between a magnetization pinned layer and a magnetization free layer both including Co. In the magnetoresistive element, a Peltier effect develops between the magnetization free layer including Co and the electrode including Au to cool down the gap therebetween.
The Peltier effect is a phenomenon discovered by Jean-Charles Peltier in 1834, and the cooling effect thereof is expressed with the following formula 1.ΔQ=Π·I·Δt  Formula 1ΔQ (C) is an amount of heat to be released or absorbed from a junction. Π is a substance-specific coefficient. Δt (s) is a time of interval for which a current has been flowed. I (A) is the current. The efficiency for cooling or heating is determined by the substance-specific Peltier coefficient, thereby requiring a proper choice for material combinations to efficiently cool down.
However, the magnetoresistive element disclosed in the Japanese laid-open patent application employs Co for the magnetization free layer to cool the Co itself, but does not have a high MR change rate owing to the Co. Therefore, a higher MR change rate cannot be expected even when cooled by using the Peltier effect.